Created basic implementation of the viewport.

The class can now hold a widget and forward calls to it. The class is
not yet complete but it looks much better now.

Also allows to switch between the naked pane and the pane in a viewport
with a #if 0.

The code is used to experiment with a different approach of the
implementation of a listbox.

src/gui/auxiliary/window_builder/listbox.cpp

@@ -106,10 +106,10 @@ twidget* tbuilder_listbox::build() const
 		tpane *pane = new tpane(list_builder);
 		pane->set_id(id);
 
-		tviewport *viewport = new tviewport();
 
 		tgrid* grid = new tgrid();
-		grid->set_rows_cols(1, 2);
+		grid->set_rows_cols(1, 1);
+#if 0
 		grid->set_child(
 				  pane
 				, 0
@@ -117,15 +117,16 @@ twidget* tbuilder_listbox::build() const
 				, tgrid::VERTICAL_GROW_SEND_TO_CLIENT
 					| tgrid::HORIZONTAL_GROW_SEND_TO_CLIENT
 				, tgrid::BORDER_ALL);
-
+#else
+		tviewport *viewport = new tviewport(*pane);
 		grid->set_child(
 				  viewport
 				, 0
-				, 1
+				, 0
 				, tgrid::VERTICAL_GROW_SEND_TO_CLIENT
 					| tgrid::HORIZONTAL_GROW_SEND_TO_CLIENT
 				, tgrid::BORDER_ALL);
-
+#endif
 		return grid;
 	}
 

src/gui/widgets/viewport.cpp

@@ -24,14 +24,137 @@
 
 namespace gui2 {
 
-tviewport::tviewport()
+/**
+ * Helper to implement private functions without modifying the header.
+ *
+ * The class is a helper to avoid recompilation and only has static
+ * functions. It also facilitates to create duplicates of functions for a const
+ * and a non-const member function.
+ */
+struct tviewport_implementation
 {
+	/**
+	 * Implementation for the wrappers for
+	 * [const] twidget* tpane::find_at(const tpoint&, const bool) [const].
+	 *
+	 * @tparam W                  A pointer to the pane.
+	 */
+	template<class W>
+	static typename tconst_clone<twidget, W>::pointer
+	find_at(
+			  W viewport
+			, tpoint coordinate
+			, const bool must_be_active
+			)
+	{
+
+		/*
+		 * First test whether the mouse is at the pane.
+		 */
+		if(viewport->twidget::find_at(coordinate, must_be_active) != viewport) {
+			return NULL;
+		}
+
+		/*
+		 * The widgets are placed at coordinate 0,0 so adjust the offset to
+		 * that coordinate system.
+		 */
+		coordinate.x -= viewport->get_x();
+		coordinate.y -= viewport->get_y();
+
+		return viewport->widget_.find_at(coordinate, must_be_active);
+	}
+
+	template<class W>
+	static typename tconst_clone<twidget, W>::pointer
+	find(
+			  W viewport
+			, const std::string& id
+			, const bool must_be_active
+			)
+	{
+		if(viewport->twidget::find(id, must_be_active)) {
+			return viewport;
+		} else {
+			return viewport->widget_.find(id, must_be_active);
+		}
+	}
+};
+
+tviewport::tviewport(twidget& widget)
+	: widget_(widget)
+{
+	widget_.set_parent(this);
+}
+
+void tviewport::place(const tpoint& origin, const tpoint& size)
+{
+	twidget::place(origin, size);
+
+	widget_.place(tpoint(0, 0), widget_.get_best_size());
+}
+
+void tviewport::layout_init(const bool full_initialization)
+{
+	twidget::layout_init(full_initialization);
+
+	if(widget_.get_visible() != twidget::INVISIBLE) {
+		widget_.layout_init(full_initialization);
+	}
+}
+
+void tviewport::impl_draw_children(
+		  surface& frame_buffer
+		, int x_offset
+		, int y_offset)
+{
+	x_offset += get_x();
+	y_offset += get_y();
+
+	if(widget_.get_visible() != twidget::INVISIBLE) {
+		widget_.draw_background(frame_buffer, x_offset, y_offset);
+		widget_.draw_children(frame_buffer, x_offset, y_offset);
+		widget_.draw_foreground(frame_buffer, x_offset, y_offset);
+		widget_.set_dirty(false);
+	}
+}
+
+void tviewport::child_populate_dirty_list(
+		  twindow& caller
+		, const std::vector<twidget*>& call_stack)
+{
+	std::vector<twidget*> child_call_stack = call_stack;
+	widget_.populate_dirty_list(caller, child_call_stack);
 }
 
 void tviewport::request_reduce_width(const unsigned /*maximum_width*/)
 {
 }
 
+twidget* tviewport::find_at(const tpoint& coordinate, const bool must_be_active)
+{
+	return tviewport_implementation::find_at(this, coordinate, must_be_active);
+}
+
+const twidget* tviewport::find_at(
+		  const tpoint& coordinate
+		, const bool must_be_active) const
+{
+	return tviewport_implementation::find_at(this, coordinate, must_be_active);
+}
+
+twidget* tviewport::find(const std::string& id, const bool must_be_active)
+{
+	return tviewport_implementation::find(this, id, must_be_active);
+}
+
+const twidget* tviewport::find(
+		  const std::string& id
+		, const bool must_be_active) const
+{
+	return tviewport_implementation::find(this, id, must_be_active);
+}
+
 tpoint tviewport::calculate_best_size() const
 {
 	return tpoint(500, 500);

src/gui/widgets/viewport.hpp

@@ -25,13 +25,41 @@ class tgrid;
 class tviewport
 	: public twidget
 {
+	friend struct tviewport_implementation;
 public:
 
-	tviewport();
+	explicit tviewport(twidget& widget);
+
+	/** Inherited from twidget. */
+	void place(const tpoint& origin, const tpoint& size);
+
+	/** Inherited from twidget. */
+	void layout_init(const bool full_initialization);
+
+	/** Inherited from twidget. */
+	void impl_draw_children(surface& frame_buffer, int x_offset, int y_offset);
+
+	/** Inherited from twidget. */
+	void child_populate_dirty_list(twindow& caller,
+			const std::vector<twidget*>& call_stack);
 
 	/** Inherited from twidget. */
 	void request_reduce_width(const unsigned maximum_width);
 
+	/** Inherited from twidget. */
+	twidget* find_at(const tpoint& coordinate, const bool must_be_active);
+
+	/** Inherited from twidget. */
+	const twidget* find_at(
+			  const tpoint& coordinate
+			, const bool must_be_active) const;
+
+	/** Inherited from twidget. */
+	twidget* find(const std::string& id, const bool must_be_active);
+
+	/** Inherited from twidget. */
+	const twidget* find(const std::string& id, const bool must_be_active) const;
+
 private:
 	/** Inherited from twidget. */
 	tpoint calculate_best_size() const;
@@ -45,6 +73,8 @@ public:
 
 private:
 
+	twidget& widget_;
+
 };
 
 } // namespace gui2